Technical Field
The present invention relates to an image forming apparatus employing electrophotography such as a copier, a printer, or a facsimile machine.
Background Art
In an image forming apparatus employing electrophotography, an electrostatic latent image is first formed in an image forming section, the electrostatic latent image is developed by toner as a developer and is rendered visible as a toner image, the developed toner image is transferred to a recording sheet by a transfer device, and subsequently, the image is fixed onto the recording sheet by a fixing device.
The fixing device include a heating member and a pressure roller that press against each other to form a fixing nip portion, through which the recording sheet on which an unfixed toner image is borne passes through. The recording sheet is pressed and heated when passing through the fixing nip, so that the toner image is fixed onto the recording sheet.
One typical fixing device for use in the image forming apparatus employs electrophotography and includes a securing member slidably contacting an inner surface of the rotary member.
Another typical fixing device employs a film heating method including: a pressure roller; an endless fixing film; a ceramic heater; and a fixing nip portion formed by pressing the pressure roller against the ceramic heater with an endless fixing film sandwiched in between. The recording sheet bearing an unfixed toner image is passed through the fixing nip portion, applies heat from the ceramic heater to the recorded material via the fixing film, to thereby press and fix the unfixed toner image onto the recording sheet.
Further another fixing device employs a belt nip method, in which an outer circumference of a running endless belt is closely contacted to the thermal fixing roller including an elastically deformable surface layer as well as the surface layer of the thermal fixing roller is elastically deformed by the pressure pad, to thus form a fixing nip portion, and the recording sheet bearing the unfixed toner image is passed through the fixing nip portion and is fixed.